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Wed, 26 Jun 2019 12:09:33 -0400 (EDT) Received: by blue.animalcreek.com (Postfix, from userid 1000) id 2FFDDA2233F; Wed, 26 Jun 2019 09:09:33 -0700 (MST) Date: Wed, 26 Jun 2019 09:09:33 -0700 From: Mark Greer To: Christoph Hellwig Subject: Re: DMA coherency in drivers/tty/serial/mpsc.c Message-ID: <20190626160933.GA28939@animalcreek.com> References: <20190625122641.GA4421@lst.de> <20190625163722.GA18626@animalcreek.com> <20190626064837.GA24531@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190626064837.GA24531@lst.de> Organization: Animal Creek Technologies, Inc. User-Agent: Mutt/1.5.24 (2015-08-30) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Mark Greer , Paul Gortmaker , linux-serial@vger.kernel.org, Dale Farnsworth , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Jun 26, 2019 at 08:48:37AM +0200, Christoph Hellwig wrote: > On Tue, Jun 25, 2019 at 09:37:22AM -0700, Mark Greer wrote: > > Yeah, the mpsc driver had lots of ugly cache related hacks because of > > cache coherency bugs in the early version of the MV64x60 bridge chips > > that it was embedded in. That chip is pretty much dead now and I've > > removed core support for it from the powerpc tree. Removing the mpsc > > driver is on my todo list but I've been busy and lazy. So, to sum it > > up, don't spend any more time worrying about it as it should be removed. > > > > I'll post a patch to do that tonight and I'm sorry for any time you've > > spent looking at it so far. > > No problem. And if future such broken chips show up we now have > support for per-device DMA coherency settings and could actually > handle it in a reaѕonably clean way. Ah, good to know - thanks. BTW, I just submitted a patch to remove the driver. Mark --